Extension Spring Initial Tension

Extension Spring Design Resources – What Is Initial Tension?

One of the least understood elements of spring design is initial tension in extension springs. So often designers will guess at the amount of force necessary to overcome this one time load, or they will disregard it entirely. Though two springs may be identical in physical size, they can vary substantially in load at a given length depending on the amount of initial tension.

A highly technical description of initial tension is coiling the spring against the plane of its own axis. However, most spring-makers simplify the description by saying that initial tension is simply the amount of force that is required to begin deflection.